Ford ’87-’96 4.9L (300) EFI Fuel Injector and Pressure Upgrades

By Edward Trethewey

Copyright 2001, All rights reserved

DISCLAIMER:It must be understood that this
upgrade should only be performed on 4.9L inline six-cylinder “race trucks”
(oxymoron?) which are only used off-highway, as this modification may have
a deleterious effect on Federally-mandated exhaust emissions limits and/or
state emissions inspections.It must be completely understood that performing
this incredibly fun and almost unbelievably effective modification is probably
a breach of Federal law and could conceivably result in both author/tinkerer
and

Always keep in mind that while no “high-performance”
version of this engine was built (even in the Land of Oz), Ford did intend
for it to be a highly reliable, high-economy, high-torque, bottom-of-the-line
truck engine, and therefore the design compromises made were conservative
in nature—want high-torque at low RPMs? Cylinder displacement! Want durability?
Seven main bearings and cam gear drive! Want cylinder block stiffness?
Thick castings throughout the head (you should see some of the outrageous
porting done on these heads--think sewer pipe). Want to make sure
your fleet driver can’t deliberately blow up an engine so he can get some
paid downtime? Use small, maxed-out fuel injectors on it, and camshaft
timing biased toward the low end (the stock cam runs out of breath promptly
at 4,000 rpm., but boy does it pull hard 1,800-3,000).

Assumptions, assuredly, but curiosity, observation,
deduction, trial-and-error, the various Internet forums, personal interaction,
initiative, and blind-melon assumptions are really the keys to effecting
performance increases from this engine, and since the engine was overbuilt
to begin with and skewed by the factory toward low-rpm torque production,
grafting on proven mild 5.0 V-8 hardware can yield astonishing results.
The trick is to enhance the stock midrange curves without losing bottom
end. Upgrading the fuel injection hardware is one of these, as are virtually
any exhaust improvements.

All of these engines (except the 4.9L) had a crossflow
cylinder head design, which places the fuel injectors a cylinder head’s
width away from the hot exhaust manifold, enabling those injectors to run
much cooler. The 4.9L has exhaust and intake ports all in a row on the
same side of the cylinder head with the injectors in a very close proximity
to the exhaust manifold, and may be subject to vapor lock when run at a
lower fuel pressure, which was one of Ford’s criteria in designing this
engine’s fuel system with a higher working pressure. One of our design
criteria is the ability of this revised fuel system to pass emissions testing
via a turned-down line pressure. The hellish Texas summertime approaches,
so we’re sure to learn all about vapor lock.

The higher line pressure may in its turn have influenced
the Ford designers to specify a 12-lb./hr. rated fuel injector rather than
the other truck engines’ norm of 19-lb./hr., and with that 7-lb./hr. difference
lies the crux of this upgrade, because the pathetic 12# units are being
replaced with the 19# (or higher) units. There is some speculation that
24-lb./hr. injectors may also be of value because of their additional capacity
to supply ultimate fuel quantity for very high horsepower engines, as the
later (’95 California/’96 50-state) Mass Air Flow (MAF) 4.9L units are
adaptable to higher flow values achievable. Supercharging, for instance.

The ’87-’95 50-state speed density versions
generate error codes (the “check engine” emissions dash light) at a relatively
low circa-40 psig, (Ford averages 39 psi across their lineup), but this
is still a very worthwhile swap. Apparently, the antiknock sensor allows
the engine to run a lot of ignition advance because the rich fuel mixture
simply won’t spark knock, which on these horribly lean low-emissions/high-MPG
engines makes an incredible difference in their power output and drivability.
We are having very good luck with our initial advance increased to 12-degrees
BTDC; stock is 10 BTDC, and we’re burning that wonderful 87 octane stuff.
We’ve mused aloud about the possibility of using higher octane and cranking
the advance way up there and been told sternly to “…not trust…”
a knock sensor too far.

End tees orientation, pipe nipples between horizontal-bull tee and end
vertical-bull tees, pipe plugs, Schrader valve, hose fitting, flare. Not
seen are two shortened 10-32 machine screws threaded upwards through bracket
bottom into tapped holes drilled in square wrench areas on two pipe plugs
in bulls of end tees..

Summit and Jeg’s both offer numerous fuel pressure
gauges, under their own logos as well as others. A 60psig or higher guage
face is what counts here. The 1.5-in. diameter underhood gauges have a
1/8” NPT spud; use the horizontal-mount type, as opposed to the vertical-mount
type.

If forced induction is in your engine’s future,
then you probably want to run an inside-mounted fuel guage. Guage pods
are available to make a clean job of mounting additional gauges inside
many popular vehicles, as are gasoline-isolating diaphragm fuel guage drives.
We highly recommend both items, especially the isolator, which gives direct
hydraulic readings but won’t let gasoline in the passenger compartment
with us—we really hate being on fire.

We went about guage-mounting the “harder” way (as
opposed the “hardest” way, which means interior-mount…cleanly…fooling around
under the dashboard…) and built a neato-looking, cheapo engine compartment
guage mounting manifold which included a Schrader valve for depressurizing
the fuel system (like stock).

These are the parts we used:

Home Depot (HD)--1 ea. joist hanger.. We used this because we had it lying
around, and wanted a small 1”x 1” x 6” light gage galvanized length of
angle on which to mount our guage manifold and with which to fasten the
assembly to the firewall.

HD—2 ea. #10 x 1” self-drilling sheet metal screws, with which to mount
our angle to the firewall. These can be longer or shorter, depending on
where you mount them and how comfortable you are about not interfering
with whatever is behind the bulkhead you mount to.

HD—2ea. stainless steel #10-32 machine screws—we got ours about 2-3” long
so we had some screw shank to hold on to when we cut shortened these screws--$0.70
for 3-in. vs. $0.50 for the shortest they had in stock (which had to be
shortened anyway, so who cares?)

HD—5 ea. stainless steel flat washers to fit the #10-32 screws.

HD—1 ea. roll of ½-inch width Teflon Tape—get the smallest
quantity available; one wrap of tape on 1/8” NPT pipe just doesn’t use
very much tape.

Auto Parts (AP)—1ea. 1/8” NPT-base Schrader valve.

AP--2 ea. 1/8” NPT pipe plugs. Brass if you can get them, square or hex
drive, either style, as long at the plug is solid inside, not hollow, and
has material enough to support threading deep enough to engage at least
four threads of the mounting screws-- Read On!

AP--3 ea. 1/8” x 1/8” x 1/8” NPT brass pipe tee. Some Plumbing 101 for
you here: stand that Tee so the single vertical stem is pointing downward,
toward the center of the earth, (We always know where we’re at—we’re directly
above the center of the Earth… at all times), and the long part of the
Tee is horizontal—just like the T in the word “Tee”. The horizontal part,
that you can sight through side-to-side, is called the “run”, and the vertical
stem is call the “bull” (no bull). Class, learn these definitions because
They Are On The Test!

AP—2 ea. 1/8” x 2” NPT brass pipe nipples.

AP—1ea. 1/8’ male NPT by –4 hydraulic flare fitting, stainless steel.

AP— “Red” Threadlocker

AP—1/2-in. size x 16-in., black plastic wiring protector wrap.

View of assembled guage manifold

Jeg’s—0-100 psi guage, P/N 656-103. These gauges all cost around around
$20.00, and come under several different manufacturer names. If it’s worth
it to you, spend another couple of bucks and get “NOS” “Holley” “Barry
Grant” or whatever—the guage is the same. We debated long and
hard: a 0-60 gauge range, or (the next step up), 0-100psi. The best of
the in-tank fuel pumps max out around 80 psi, making the capability of
the 100 psi guage possibly necessary. The downside of the 1-100 guage is
that the gradations are smaller than a 0-60, and harder to see, so accuracy
suffers.

Jeg’s—1 ea. 1/16” male NPT x –4 hydraulic/fuel flare fitting, P/N 741-179-45,
NOS-brand. We’ve never heard of 1/16 NPT before, but that is the thread
size Ford used on the fuel pressure relief Schrader valve on the fuel rail
of 4.9L trucks and Mustang 5.0s, and presumably other EFI motors as well.
We bought ours from a local dyno/high tech motorsports place under the
“NOS”-brand…the counterman there (as well as at “Jeg’s”) was well-familiar
with “…that weird fitting Ford uses…”

Jeg’s—1 ea. 16-inch –4 high pressure steel-braided teflon-lined hose with
stainless steel female-swivel ends, Aeroquip or Russell are good sources.
Jeg’s has a prepackaged 12-inch “Nitrous Works” (P/N 113-24412) which meets
this spec, but in our opinion it is a little too short to enable us to
make the clean, gentle-radius corners we prefer, en route from the fuel
rail takeoff point up and back to the firewall.

Start off by wrapping male threads (NPT only) with
ONE WRAP of Teflon tape, beginning ONE THREAD back from the threading where
it begins to thread into the female-threaded hole. We’ve heard it said,
often enough, that several wraps of tape make for a better seal, as though
Teflon tape has some sort of intrinsic, magical sealing power—it doesn’t,
all it does is reduce friction, thereby allowing a deeper thread penetration
at the same torque load. And by starting back one thread, the chance of
a frayed fragment of tape detaching itself and worming its way into the
fuel injection system’s ultra-precise works is reduced.

Thread the two nipples into the runs (I told you!)
of the tees, such that a tee, bull downward, nipple, tee bull horizontal,
nipple, tee bull downward pattern is established, making sure that there
is exactly a 90-degree difference in bull orientation between the two end
tee’s bulls, which as a finished product will point at six o’clock, the
central horizontal bull at 3 o’clock (or 9 o’clock).

Measure the total length of the two pipe plugs, and
transfer that measurement LESS 1/16-inch (or so) to the 10-32 drill bit.
Wrap a length of tape around that drill bit at this measurement so that
maximum depth is marked and easily seen and is achieved without perforating
the plug…gasoline under high pressure will be contained within the guage
manifold and back behind these not-completely-drilled-through plugs! Tap
each pipe plug 10-32, as far as possible. Thread into the bulls of the
two tees having a vertical orientation.

Cut a straight length of light-guage metal angle 1”
tall, 1” wide, and 6” long. On its back (or vertically-oriented) side,
this angle will mount to the firewall, and the bottom (horizontal-orientation)
will form a surface to which the fuel guage manifold is anchored.

Measure exactly the mean distance between the pipe
plugs, and transfer that measurement to the horizontal mounting “shelf”
formed by the angle, so that the fuel guage manifold is centered in both
the length and width of the angle. Drill those holes ¼-in. dia.

Shorten the two 10-32 screws so they bottom out in
the pipe plugs using one flat washer each, but not the angle. The added
thickness of the angle when assembled will ensure proper torque without
thread-bind at final assembly time.

Mock-up the fuel guage manifold on the bracket, and
mark the back of the bracket for holes for the two #10 sheet-metal screws
that that will fasten the assembly to the firewall, keeping in mind that
a screwdriver has to be held nearly horizontal to turn the screws, then
drill those holes, too.

Countersink all holes, finish all edges, clean in
lacquer thinner, and, if galvanized, smear on some cheapo 5% white vinegar,
which will etch the surface and enhance paint adhesion, ‘cause it’s time
go go blow some paint on the angle, the four screwheads, and the guage
manifold (plug the two end holes and center guage hole with toilet paper,
masking tape if you’re a high-roller). We used ‘60’s Ford engine blue.

Final-assemble the guage manifold to the angle, using
copious amounts of the threadlocker plus one flat washer per screw. Remember
how those four ¼-in. dia. holes were bigger than the 10-32 but smaller
than the o.d. of the washers? Gee, it all went together easily! (If
you
can drill same-size accurately-spaced holes, well…)

You’ve been itching to do this one…go ahead and screw
that new, chromed and high-perfed-logo guage in—WITH THE CORRECT OPEN-ENDED
WRENCH ON THE WRENCH-SQUARE AT THE BACK OF THE GUAGE, not with pliers around
the periphery of the guage case! It is only too easy to ruin a delicate
guage, so don’t get ham-fisted (drink decaf coffee, not beer); NPT means
“National Pipe Taper” meaning the shank of an NPT nipple is gradually tapered,
wedge-shaped in profile, and gets progressively tighter as it is screwed
inward. The mounting spud of this guage, like most of the rest of the assembly,
is 1/8” NPT brass; some judgement , “feel”, is required to get a., enough
torque without too much torque on this guage fitting, and b., correct orientation
of the guage’s face so that the numbers midpoint of its travel are in the
12 o’clockpoint position; i.e., “50” psi should read at the top of a 0-100
guage; “30” psi likewise in a 0-60 piece.

A vertical-mount guage could be used, but to our mind
the assembled guage manifold unit is too tall, and takes up too much firewall
room vertically.

Using the correct backup combination of box end and
line wrenches and being very careful not to disturb the 90-degree difference
in all the tee’s orientation, assemble the Schrader valve to the driver’s
side end tee’s run, and the 1/8” x –4 flare to the passenger’s.

Relieve pressure on the engine’s fuel rail via the
stock Schrader valve—conveniently located near #6 cylinder, nestled inside
the curve formed by the EFI air manifold tubes, close to the firewall.
Try not to spew gas everywhere; self-immolation went out with the ‘60’s—try
not to reinvent a questionable fad! Catch any pressurized gas with a rag
(and then dispose of it, muy pronto!) As always when working on a fuel
system, have a fire extinguisher close to hand.

Unscrew the stock Schrader, and screw in the
special Ford-size flare fitting, snugly but not excessively tight—those
threads are small! We used no Teflon tape here. Dispose of that Schrader;
it won’t fit anything else, anywhere.

Hand-tighten the braided hose so that it will swivel
freely without coming off fuel rail fitting, and gently, thoughtfully,
route it through the air manifold between runners #5 and 6, then up and
backwards outside the heater core box, then curve around so the other end
swivel fitting is aligned horizontally at the firewall, pointing toward
the spark plug side of the engine.

Loosely screw the hose to the guage manifold, align
that puppy so it is horizontal and high enough on the firewall to be easily
seen, fasten the bracket-to-firewall screws, and using two wrenches, tighten
the swivel fittings, then leak test your work by turning the ignition key
to “On” but not “Start” (you can hear the in-tank pumps pressurizing the
system). Leaving it “On”, go eyeball your pipe joints, then test with a
dry finger, NOT A LIT MATCH!

There are a lot of detail similarities between the
small-block V-8 engines and the 300-6, which is not too surprising considering
they originated during statistically the same timeframe, early-to-mid Sixties,
from the same manufacturer, with probably quite a bit of design department
interface. There is a high percentage of commonality in small part; volume
production with the smallest degree possible of variation from the basic
design an economic imperative; look at Ford’s current Modular Engines—that
are used across a dozen brand names and in myriad uses, high-winder Eurocar
to heavy-duty truck. We rest our case!

Installing a 5.0 Mustang adjustable fuel pressure
regulator is nowhere near as complicated as we made the guage installation.
Go buy:

We suppose it’s possible to change regulators without
removing the upper air manifold and appurtenances, but we unlucky enough
to be hatched without the eight fingers for each of three or four hands
jointed by quadruplicate elbows required, so we pulled the upper manifold.
Begin by pulling off the air cleaner tubes, throttle body, EGR from T/B,
and that upper air manifold. Clean that mating flange well, and when pulling
that upper manifold, pull straight up! There are a couple of easily-broken
plastic dowel pins locating gasket and manifold.

Also, the Thermactor (you know: air pump, smog pump,
@#$%^&*() pump, etc.) vacuum and pressure connections and numerous
other vacuum connections will have to be disconnected.

Ford Motor Company, in its infinite wisdom, has equipped
modern vehicles with numerous vacuum-operated emissions devices, fed through
1/8 dia. plastic hoses often bundled together and/or in with wiring harnesses.

These small plastic vacuum pipes embrittle with heat,
oily vapor, and time (obviously; they belong in a long-lasting motor vehicle,
right?) and therefore, when disturbed, break with only the smallest provocation.
Only seriously disturbed citizens soup up their six-cylinder pickups, so
plan on using up some of that copper line and 1/8 i.d. rubber hose you
were told to go get. Or don’t.

Upper manifold off (that last bolt by the firewall
was a “challenge”, wasn’t it?), get the that Allen wrench, remove and fling
stock regulator and weirdo allen bolts in the trash, where they belong.

Rip your cool new adjustable unit out of its blister
packaging with the Crane Cams logo (on the packaging, not the regulator…somebody
else makes it, Crane just markets it--cheaply), and plug it into the fuel
rail. We’re using the Crane Cams piece because the vacuum reference hose
slides down over the pressure adjusting screw, which has a small hole drilled
in it. The hose hides the fact that it is adjustable, which to our paranoid
mind is a Good Thing come emissions inspection time.(PHOTO 6)This
is not such a Good Thing if you want to make adjustments with the engine
running and vacuum reference hose connected, and there are other AFRs out
there with a separate vacuum nipple.

The good news is, the pressure and return spuds and
base gasket all match up perfectly, same-same, which is what really matters.

The bad news is, the new regulator’s base flange is
smaller, shaped differently, has a way-different bolt pattern, and the
flange is internally-threaded so its hold-down screws thread from the bottom
upwards through an unthreaded fuel rail mounting pad, whereas the I-6 fuel
rail mounting pad is internally threaded, and the stock regulator’s mounting
flange is undrilled, the screws threading downward.

A retroactive review of “Ford Electronic Fuel Injection
Systems” confirmed this—all the pictures of different I-4, V-6, and V-8
engines used the bottom-upward bolting system.

We know that you really wanted to know that.

The 4.9L fuel rail regulator base is much larger physically
that the 5.0L AFR, so it would be possible to simply drill and tap two
new holes (of three required) in the 4.9L fuel rail’s regulator mounting
pad. This leaves the third mounting hole in the new regulator hanging off
in space, with nothing to secure it to—and since the base is triangular,
all three mounting holes have to be used to ensure an equal clamp load.
We suppose that we could have devised some sort of clamping strap to pass
underneath the fuel rail, but that’s tacky and besides, we’d have to drill
and tap two additional holes in that mounting pad--and we really don’t
like the idea of drilling holes that closely to the fuel rail inlet; microscopic
metal shavings have a way of migrating into fuel injectors!

We elected to do something simpler, cleaner, and far
more elegant.

The regulator is barrel-shaped, the two halves crimped
together circumferentially at the widest part of the “barrel”, a perfect
place for a hold-down flange.

Note different mounting flanges, mounting method,
vacuum reference elbow, 1.5” hole in center of 3” dia. flange—the pressure
adjusting screw has a small hole drilled through its middle, 19-lb./hr.
injectors, all in a line, hold-down flange. Partially obscuring injector
#1 is the infamous #1 fuel rail bracket that didn’t get adequately tightened!
Look carefully and you’ll note we were living dangerously in this picture
and weren’t at that time using Nyloc backup nuts underneath hold-down screws!

The idea is go buy a 4” by 4” hunk of .125” thick
mild steel plate. The thickness, material, and size really doesn’t matter
as long as it is inflexible and can take a 3-inch outer diameter cut.

The first step is to lay out what is essentially a
big, flat, washer with three ¼” dia. holes in it that correspond
to the threaded holes in the regulator’s mounting pad on the fuel rail,
and drill them.

The second step is to is to holesaw the 1-1/2” central
hole which will slide easily but snugly over the new AFPR.

The third step is to make the 3” outer holesaw cut,
at which point the rough-in work is done. Go countersink, deburr, and paint
your new masterpiece of machine art.

Paint dry, mount the flange using all the #10-32 machine
screw hardware mentioned above, with plenty of Loctite. The factory holes
probably have metric threading, but the #10-32s screw in there though just
a smidge looser than is ideal. The threadlocking compound and the Nyloc
backup nuts make that irrelevant.

This is a no-brainer; you can’t screw it up (we did,
naturally!) All six injectors seat (float, actually) in drilled pockets
in the lower air manifold, sealed by thick “O”-rings, tips pointing at
the respective intake valve, and are held in place from above by the fuel
rail, which in its turn is bolted to the same air manifold by THREE bolts.

Remove the bolts, and gently work the fuel
rail off the injectors. There is enough play in the fuel delivery and return
lines to make this possible without disconnecting the A/C-type garter fittings
back by the firewall, which is a major PITA. Unhook the Weatherpack electrical
connectors (oh-so-gently; the plastic clips love to break).

Pull the old injectors from both air manifold
and fuel rail, clean fuel rail and air manifold injector pockets, lightly
lube all new “O”-rings and all pockets, and gently work the injectors
into their respective manifold pockets and the fuel rail onto them.

Reinstall all three bolts, torque all three
bolts to 18-ft./lbs; read that last sentence again.

Take a good look at the fuel rail mounting bracket
in the vicinity of injector #1, just beyond the 180-degree curve taken
back toward the firewall by the fuel rail. Certain brainless wonders left
that bolt loose. Consequently, the slight freeplay allowed between bracket
and mounting pad by that oversight enabled gasoline pressurized at 55 psig
to spit the upper “O”-ring out after a couple of days, and spew gasoline
so hard into the windings of the alternator that it shorted out temporarily,
scaring us somewhat.

In fact, down here in Texas, they call that kind of
scare a “brown pants special” or “trouser chili”.